LONDON The U.S.-led coalition's offensive to oust Islamic State from the Syrian city of Raqqa killed more than 1,600 civilians, according to the results of an investigation, released jointly Thursday by Amnesty International and the group Airwars.

The report said the deaths were a direct result of "thousands of U.S., U.K., and French air strikes and tens of thousands of U.S. artillery strikes in Raqqa between June and October of 2017.

"Coalition forces razed Raqqa, but they cannot erase the truth," said Amnesty International's Donatella Rovera. "Amnesty International and Airwars call upon the Coalition forces to end their denial about the shocking scale of civilian deaths and destruction caused by their offensive in Raqqa."

Airwars director Chris Woods called on the coalition to "fully investigate what went wrong at Raqqa and learn from those lessons."

A Pentagon spokesman, in an email to VOA, said, "The Coalition complies with the Law of Armed Conflict and has taken extraordinary measures to minimize civilian casualties and collateral damage. We look at any and all sources for allegations of civilian casualties to include self-reports, social media, NGOs, news organizations and personal allegations.

A U.S.-led coalition spokesman provided a much lower death toll from Raqqa.

"According to our records, there have been 69 credible allegations out of Raqqa, resulting in 318 killed. Of note, there are still open allegations under investigation. Amnesty International provided us with 86 new allegations, 43 of which had already been assessed as credible and previously reported or were deemed not credible because the allegation did not corroborate with our strike records," said Col. Scott Rawlinson." We requested that Amnesty International provide us with additional information on the remaining 43 allegations if they have it so that we would be able to determine whether we could conduct an investigation."

Researchers for Amnesty and Airwars combined firsthand accounts on the ground with open source and satellite data to identify individual air strikes and victims.

Following a two-year investigation, Amnesty says it has gathered names for more than one thousand of the victims and claims to have verified 641 deaths on the ground in Raqqa

This is not a situation of a few individual cases, isolated cases. It is much more systemic than that, said Rovera.

The IS militant group seized Raqqa in early 2014 and was defeated by U.S.-backed fighters earlier this year. During its control of Raqqa, IS conducted mass killings and enslaved minorities, actions the United Nations said amounted to genocide.

The battle for Raqqa was "marked by violations committed by all sides and came at an extremely high cost to civilians," U.N. human rights experts said in a report last year.

Amnesty's Rovera said that the weaponry used in Raqqa meant some of the coalition strikes were effectively indiscriminate.

U.S. forces boasted that they had used more artillery in Raqqa than in any place at any time since the Vietnam war. And that is nothing to be proud of because the risk for civilians is unacceptable. And on the air-delivered munitions, the munitions were precise but any precision munition is obviously only as precise as your intelligence, she said.

Amnesty says it has previously documented how Islamic State used civilians as human shields in Raqqa, mined exit routes from the city and shot at those trying to flee.